[lwip-devel] [bug #48328] Fatal RST/ACK loop caused by commit "fixed bug #48170"

[Ambroz Bizjak]

Follow-up Comment #8, bug #48328 (project lwip):

Hey,
Just a remark. I'm reading the TCP RFC (793) and I think the specs under Event
Processing actually contradicts the more informal description on reset
handling on page 37, which lwIP supposedly violates.

On page 69, acceptability of a received segment is defined, which does indeed
classify out-of-sequence RSTs as acceptable. However, there is also this
text:

"In the following it is assumed that the segment is the idealized segment that
begins at RCV.NXT and does not exceed the window. ..."

And since the RST checking (page 70, 71) is specified after this,
out-of-sequence (but in-window) RSTs should be dropped or buffered for later
processing, rather than abort the connection immediately. On the other only
non-acceptable (according to the exact definition on page 69) RSTs should be
ACKed.

lwIP could be changed to be more compliant in that respect.

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